/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
 
* http://www.apache.org/licenses/LICENSE-2.0

* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/

grammar Urn;

URN: 'urn:' NID ':' NSS;
fragment NID: LETNUM LETNUMHYP+; // TODO limit to {1,31}
fragment LETNUM: [a-zA-Z0-9];
fragment LETNUMHYP: LETNUM | '-';
fragment NSS: URNCHARS+;
fragment URNCHARS: TRANS | '%' HEX HEX;
fragment TRANS: LETNUM | OTHER;
fragment HEX: [a-fA-F0-9];
fragment OTHER: '(' | ')' | '+' | ',' | '-' | '.' | ':' | '=' | '@' | ';' | '$' | '_' | '!' | '*' | '\'';
